Taking a look at fouling in bioethanol production

Thursday, October 15, 2015

There are few things more frustrating than having to deal with faulty equipment. This is true for an office job, construction worker, teacher and even bioethanol producers.

The deposition of solids on the inside surface of processing equipment is commonly known as fouling in the biofuel industry. The solids interfere with the proper operation of the equipment and reduce flow capacity and increase pumping costs.

To assist producers with fouling issues, Rob Whitely, head of the school of chemical engineering at Oklahoma State University, proposed a study to the Department of Transportation-Research and Innovative Technology Administration through the South Central Sun Grant Program, which was approved in 2013. Whiteley, also a researcher in OSU’s Biobased Products and Energy Center, is excited about some of the revelations found in the study.

“The impact of fouling on the production of bioethanol from corn is well known,” he said. “The extent to which fouling is a problem in a sweet sorghum-ethanol industry is an unknown.”

The study, “Multi-scale Fouling Characterization of Fermented/Hydrolyzed Sweet Sorghum,” answered a key question regarding the economic viability of decentralized production of sweet sorghum as an energy crop. The amount of solids in fermented sweet sorghum is approximately 2 weight percent, compared to 20 weight percent in fermented corn mash.

“Based strictly on solids content, one would expect the fouling problem using sweet sorghum to be 10 times less than that of corn,” he said.

However, Whiteley and his team have not observed any significant fouling to date in their farm-scale Alcohol Separation Unit. This result has been confirmed in the laboratory, where no significant fouling was measured in a heat exchanger tube (one of the most likely deposition locales).

“In fact, our studies showed that fouling from fermented sweet sorghum was no greater than that measured for tap water,” Whiteley said. “We attribute this finding to the fact that the sweet sorghum bioethanol process is essentially starch-free.”

These results confirm the production of bioethanol from sweet sorghum can be accomplished without the costly downtime and maintenance associated with corn-ethanol.

“This increases the global transportation energy portfolio and provides economic development opportunities for the state of Oklahoma and similar regions in the world,” Whiteley said. “Increasing the number of sustainable energy production options is essential to meet the demands of a growing world population.”

Whiteley acknowledged Anuradha Mukherjee, a graduate student who recently completed her Ph.D. degree, who helped design, build and operate the ASU for her dissertation research.